I just encountered this problem with a fresh install of the latest version. I was trying to compare a backup file from SQL Server 2000 with a live database. This generated the described error, but interestingly when I restored this database on the same server and compared there was no such problem. This might be suitable for some people encountering this problem, and suggests that there might be variation between the backup handling and live database handling (perhaps the "fix" can be copied between these sections of the program?).